Because Reno was told no.
https://www.kunr.org/post/trump-rally-reno-canceled-due-covid-19-restrictions#stream/0
The population in a 20 mile radius won’t matter, trust me. I drove over 200 miles one way to go to a hangar rally in 2016.
If there’s only 50 people allowed max, including reporters and Secret Service, then maybe Trump is going to look at the wildfires? Or something like that?